1. Field of Invention
The present invention relates to a flat shield cable. In particular, the invention relates to a flat shield cable that is suitably used for electrical connection to electric equipment, etc. of vehicles such as automobiles.
2. Description of Related Art
In vehicles such as automobiles, many shield cables are used for electrical connection to electric equipment, etc. In recent years, flat shield cables have come to be used from the viewpoint of space saving, etc. FIG. 1 shows the structure of an exemplary conventional flat shield cable.
This conventional flat shield cable 1 has a flat structure in which a plurality of signal lines 2 each having an insulating cover and a drain line 3 are arranged parallel with each other and the signal lines 2 and the drain line 3 are covered with a shield layer 4, which is covered with an insulating sheath 5.
With this structure, external noise is interrupted by the shield layer 4 and led to an external ground via the drain line 3, whereby good signals are supplied to various kinds of electric equipment through the signal lines 2.
Incidentally, to improve the transmission characteristic (characteristic impedance) and reduce the weight, it is desired that the cross-sectional area (hereinafter also referred to as “conductor size”) of the core conductor of each signal line 2 be as small as possible (e.g., 0.08 mm2 or 0.13 mm2). However, if the conductor size of each signal line 2 is reduced, the strength lowers to raise fear that a disconnection may occur in outside signal lines 2 when the cable 1 is bent in the width direction.
For example, in a flat shield cable in which two signal lines 2 and a drain line 3 are arranged parallel with each other and the conductor size of each signal line 2 is 0.08 mm2, when bending stress is exerted on the flat shield cable 1 in the width direction to cause a bend, the core conductors of the outside signal line 2 is elongated by the bending. When the cable 1 is bent further, a disconnection occurs in the core conductor of the outside signal line 2. Break strength at that time was 53 N.
As described above, in the conventional flat shield cable 1, reducing the conductor size of each signal line 2 makes the cable 1 prone to a disconnection due to bending. This means a problem that wiring work needs to be conducted with sufficient care so as not to cause a bend.
Another problem encountered is the removal of the insulating sheath from the shield layer. In a conventional cable, the insulating sheath and the shield layers are adhered in a manner to inhibit removal, thus complicating repairs.